Is saying "yes" in response to the question "Are you God?" in the context of joking and teasing considered shirk (associating partners with God), especially with the knowledge of Allah's saying: "Indeed, Allah does not forgive association with Him"?

A person's statement about himself that he is God is a major act of disbelief (kufr akbar) that expels him from the fold of Islam, whether he is serious or joking. This is because joking about disbelief is disbelief itself. And whoever utters a word of disbelief willingly has opened his heart to it. It is obligatory for the one from whom this emanated to repent to Allah Almighty, feel remorse, resolve not to return to such a statement, and to frequently seek forgiveness and perform righteous deeds.